A nitride semiconductor has a feature that it has a high breakdown voltage, a low resistance, and a high speed operation in comparison with a silicon semiconductor. For example, in a nitride semiconductor-based transistor having a hetero-structure called a High Electron Mobility Transistor (HEMT), a two-dimensional electron gas is formed in a hetero-junction portion. The two-dimensional electron gas has high electron mobility and a high electron density. Therefore, it is possible to fabricate a device that has a low resistance and a high speed when the nitride semiconductor is used. This enables the device to be downsized and a parasitic capacitance within the device to be reduced. However, when the parasitic capacitance is reduced, there are problems in that static electricity is not absorbed within the device and a resistance of the device against the static electricity is decreased.